Gastric carcinoma is a major cause of cancer related mortality world wide. The disease is more common in Japan with an incidence of 70 cases per 100,000 populations per year. Prognosis of the disease is poor due to late presentation. Better outcomes have been obtained in Japan due to early detection of the disease.
Classification:
Gastric cancer can be divided into early and advanced gastric cancer.
Early Gastric cancer: is defined as lesion confined to mucosa and submucosa regardless of the presence or absence of perigastric lymph nodes (T1, and N). In Japanese classification early gastric carcinoma can be classified as protruding, superficial and excavated lesions.
Early gastric cancer is thought to be curable disease and 5% survival rate is more than 90%.
Advanced gastric carcinoma: Advanced gastric carcinoma is a neoplasm that has
extended submucosa and muscularis propria.
Bormann has classified advanced gastric cancer into four types:
Type 1: Polyploid, well demarcated.
Type 2: Ulcerated with sharply demarcated margins.
Type 3: Ulcerative without definite margins.
Type 4: diffuse infiltration without significant ulceration.
Histopathology:
Adenocarcinoma (95%)
Lymphoma (4%)
Malignant GIST
Lauren has classified adenocarcinoma into intestinal type and diffuse type. Intestinal type
form polypoidal mass or ulcer, while diffuse gastric cancer infiltrate deeply without forming obvious mass and carries poor prognosis
Causative factors
Diet nitrites derived from nitrates may undergo nitrosation to form nitrosamines and nitrosamides (which are carcinogenic).
Smoked food.
Excessive salt.
Decrease intake of fresh vegetables.
Chronic gastritis (H - Pylori)
Pernicious anemia.
Previous gastric surgery like gastroenterostomy. (Duodenogastric reflux increases chances of gastric malignancy four times than normal population.
Mutation of E-cadherin (diffuse gastric carcinoma)
Spread of gastric carcinoma:
Gastric carcinoma spreads by direct invasion, lymphatic channels, and blood vessels and
through transperitoneal.
Direct Spread: Pancreas, colon, liver.
Lymphatic spread: 420 lymph nodes have identified and involvement of 4 or more lymph
nodes are poor prognostic indicators. Note that lymph from all areas of the stomach ultimately reaches the celiac nodes. From here it passes through the intestinal lymph trunk to reach the cisterna chyli.
Surgical Importance of Lymphatic drainage
The extensive lymphatic drainage of the stomach makes the removal of complete cancer difficult.
Involvement of nodes along splenic vessels can be dealt with by removing spleen, gastrosplenic and lienorenal ligament, the body and tail of pancreas.
lymph nodes along gastroepiploic vessels can be removed by excising the greater omentum.
However involvement of nodes along the aorta and head of pancreas may render the growth non-resectable.
Lymphatic spread can also occur through cisterna chyli to involve left supraclavicular lymph nodes (Virchow's Node)
Blood Borne Spread: Liver, lungs and bones.
Transperitoneal spread: Into periumbilical lymph nodes (sister marry Joseph nodules),
ovary (Krukenberg tumor), into a pouch of Douglas (Blumer shelf) which may be palpable during digital rectal examination.
Clinical features:
Early gastric cancers are usually asymptomatic.
In advanced cancer there may be bloating, distention and vomiting.
Every patient over the age of 45 years presenting with dyspepsia should undergo endoscopy before starting the treatment.
The most common cause of late presentation is liberal use of H2-receptor antagonists and proton pump inhibitors as these drugs relieve the symptoms of malignancy as well.
There may be a palpable epigastric mass which signifies incurable disease.
Tumor may bleed leading to iron deficiency anemia.
Tumor may perforate leading to peritonitis.
Obstruction leads to dysphagia and persistent vomiting (gastric outlet obstruction).
Physical signs:
These signs are usually associated with advanced or metastatic disease. These are following:
Palpable abdominal mass (epigastrium).
Palpable supraclavicular lymph nodes (Virchow's node).
Palpable periumblical lymph nodes (Sister Marry Joseph nodules).
Palpable ovarian mass (Krukenberg tumor)
Palpable mass on digital rectal examination (Blumer shelf)
Investigations:
Gastroscopy:
Fiber optic gastroscopy is the gold standard investigation for diagnosis and screening. Exact site of the tumor can be located and biopsy can be obtained to establish tissue diagnosis. In case of high index of suspicion if biopsy turns out to be negative for malignancy, patients should be re-endoscoped and more aggressive biopsies (upto 10 from different areas) should be obtained.
Endoscopic Ultrasonography:
Endoscopic ultrasonography helps to define the limit of spread of gastric cancer into the gastric wall and it can also identify lymph node involvement.
CT scan abdomen, pelvis and chest:
CT scan abdomen, pelvis and chest provide useful information regarding local extent of the tumor, lymph nodes involvement and systemic metastasis (liver, lungs). These valuable
information plays a key for treatment planning.
MRI does not confer any additional benefit.
PET scan: it is increasingly being used in the preoperative staging of gastro esophageal cancer, as it often demonstrates occult spread (10%), which renders the patient surgically incurable
Pre-operative laparoscopy: is not a common practice but sometimes can change the operative plan if small peritoneal implants or small liver metastasis are found that were not detected on preoperative imaging techniques.
International union against cancer (UICC) staging of gastric cancer:
T1: Tumor involves lamina propria.
T2: Tumor invades muscularis or subserosa.
T3: Tumor involves serosa.
T4: Tumor invades adjacent organs.
NO: No lymph nodes.
N1: Metastasis in 1-6 regional nodes.
N2: Metastasis in 7-15 regional nodes.
N3: Metastasis in more than 15 regional nodes.
MO: No distant metastasis.
M1: Distant metastasis (this includes peritoneum and distant lymph nodes).
Treatment:
Surgery is the only effective treatment which offers a chance of cure or long term survival. It is important that patients with incurable disease should not be subjected to radical surgery.
Signs of incurability include:
Hematogenous metastasis like lungs, liver and bone involvement.
Involvement of distant peritoneum.
Involvement of structures that cannot be removed.
Subtotal gastrectomy:
The standard operation for gastric cancer is radical subtotal gastrectomy provided it achieves adequate tumor clearance (5cm tumor free margins).
Subtotal gastric resection includes:
ligation and division of right and left gastric and gastroepiploic arteries at the origin,
en block resection of distal stomach (75-80%) including the pylorus and 2cm of the duodenum.
The greater omentum, lesser omentum and associated lymphatic tissue is also removed. Transverse colon, spleen or pancreas may need removal if involved locally by the tumor.
Reconstruction is usually performed by Billroth II gastrojejunostomy or roux-en-y reconstruction.
The above mentioned operation can also be performed laparoscopically.
Total gastrectomy:
More proximal tumors require total gastrectomy with esophagojejunostomy as shown below.
Extent of lymphadenectomy:
The Japanese research society for gastric cancer has numbered the lymph nodes stations that potentially drain the stomach.
D1: D1 are the perigastric lymph nodes; along the greater and lesser curvature and around the pylorus (stations 3, 4, 5, 6).
D2: D2 includes nodes around left gastric artery splenic artery, common hepatic artery and nodes around cardia. (Stations 1-8 and 11 are removed)
D3: This include lymph nodes around celiac axis (9) splenic hilum (station 10), nodes around right and left hepatic artery and porta hepatis (station 12), nodes behind the head of pancreas and aortocaval lymph nodes to some extent. (Station 1-12 are removed) Much better long term survival has been reported from Japan with D2 resection
Total gastrectomy:
A total gastrectomy is needed in the following situations.
When proximal distance from the cardia is less than the required length to achieve safe tumor free margins.
When Neoplasm involves two or three sectors of the stomach.
Diffuse carcinoma (Bormann 4) irrespective of size.
Along with total gastrectomy, omentum and D2 lymphadenectomy should be performed. The
adjacent organs like spleen, pancreas, and transverse colon may also need removal if
involved. Gastrointestinal continuity is obtained by Roux-en-y esophagojejunostomy.
Palliative treatment:
Palliative treatment is all that is required in the majority of patients because the patients usually present at a late stage when the time for curative resection has usually passed, so palliative treatment is needed to relieve the symptoms of the patient. In these cases palliative gastrostomy or gastrojejunostomy may be helpful. For inoperable tumors situated at cardia, intubation or stenting may be valuable to relieve the obstruction. Feeding jejunostomy may sometimes be needed.
Complications of Gastrectomy:
Complications of surgery:
Hemorrhage.
Wound infection.
Leakage of anastomosis.
Leakage from duodenal stump leading to paraduodenal collection and biliary peritonitis.
Nutritional complications:
Vitamin B12 deficiency due to loss of intrinsic factor leading to anemia.
Dumping, diarrhea (less common than in gastric ulcer surgery).
Bone disease:gastric surgery may disturb calcium and vitamin-D metabolism as calcium absorption occur mainly in duodenum which is bypassed Billroth II gastrectomy
Other treatment modalities for gastric carcinoma:
Radiotherapy:
Radiotherapy has a very limited role in gastric carcinoma. Radiotherapy can be helpful to relieve bony pain caused by metastasis in the bones.
Chemotherapy:
Gastric cancer may respond to cytotoxic therapy. Chemotherapy can also be used before surgery for inoperable cases to make them operable. The usual combination is
Epirubicin, Cisplatinum and 5 fluorouracil.
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